Water-tube boiler



WATER-TUBE BOILER Filed Feb. 4, 1937 6 Sheets-Sheet 1 July 9, 1940. wLEw|s WATER-TUBE BOILER Filed Feb. 4, 1937 6 Sheets-Sheet 2 h Xian/ZSJuly 9, 1940. w. Y. LEWIS WATER-TUBE BOILER Filed Feb. 4, 1937 6Sheets-Sheetfi DO00 nOO 00006 0 July 9, 1940. w. Y. LEWIS WATER-TUBEBOILER 6 Sheets-Sheet 4 Filed Feb. 4, 1937 July 9, 1940. w w s 2,207,321

WATER-TUBE BO ILER Filed Feb; 4, 1937' a Sheets-Sheet 5 July 9, 1940. w.Y. LEWIS 2,207,321

WATER-TUBE BOILER Filed Feb. 4, 1957 6 Sheets-Sheet e Patented July 9,1940 WATER-TUBE BOILER William Yorath Lewis, London, England ApplicationFebruary 4, 1937, Serial No. 124,106 In Great Britain February 7, 1936 2Claims. (01. 122-444) The invention relates to water-tube boilers of thekind having a steam drum with tubes passing in a downward directiontherefrom.

According to one form of such a boiler, a single drum is provided fromwhich banks of tubes pass in a downward direction so as to form ineffect an inverted V.

It is well known that in such a boiler and in many other types ofwater-tube boiler, the few front rows of tubes exposed to radiant heatand on which the hot gases first impinge absorb a very considerableproportion of the total heat transmitted and that the efliciency ofsucceeding rows falls off rapidly until in the case of the rows furthestfrom the furnace it reaches a very low figure.

The present invention has forits main object to provide improvedarrangements for supplying comparatively cold feed water whereby thecold feed passes through the inner tubes of the outermost row of tubes,the latter being kept at a comparatively low temperature, thus providinga substantial temperature difference between the furnace gases and thosetubes.

With such an object, the present invention consists in a water-tubeboiler comprising the combinations of elements hereinafter. describedand particularly pointed out in the claims.

Referring to the accompanying drawings which are of a diagrammaticnature Figure 1 is a half cross-sectional elevation on the line ll ofFigures 6 and 7 of one form of the boiler as seen from the front,

Figure 2 being a corresponding half cross-sectional elevation on theline 2-2 of Figures 6' and '7 as seen from the rear of the boiler;

Figures 3 and 4 show one arrangement of the feed pipes in elevation andplan;

Figure 5 shows in cross-section a detail of the drum and attachments toa larger scale;

Figure 6 is a half sectional plan on the VIVI of Figure 5, and

Figure 7 'a corresponding view on the line VIIVII of Figure 5; while IFigure 8 is a diagrammatic view of a boiler shown in the above figuressuperposed on a water-walled combustion chamber.

In carrying the invention into eifect according to one specific form asshown, the boiler is of the inverted-V type above indicated, having asingle drum, 2, fitted with dependent U-tubes, 3, attached at theirupper ends to the steam drum while their lower ends are carried in slotsor other apertures in a vertical supporting plate l2 or the like.

tion, the banks of tubes on the two sides of the boiler are similar inconstruction and for convenience only one side will be described.

The first few, say four, rows of tubes, A, that is those nearer thefurnace, are of the U-Field type with theirjouter tubes secured to thewall of thesteam drum, 2, and their inner tubes, 3a, associated with aninternal drum, trough or the like, 4, running longitudinally. Beyondthefirst few rows, A, a space is left for the accommodation of asuperheater, B.

Beyond the superheater again are, say four rows, 0, of U-tubes andfinally, six or eight more rows,D, of U-tubes serving assensible-heating means. These latter rows, C and D, of tubes have theirlegs, 3, secured to the wall of the steam drum while feed tubes, 3a, aresecured to the stepped wall of a feed-box, 5, running within the maindrum from end to end and adjacent to its relevant side wall.

' The plane of each U is disposed at a right angle or some other angleto the axis of the drum so that the U-legs are at different distancesfrom the furnace, while the feed tubes, 3a, are aligned with the legs ofthe Us more remote from the furnace, the feed tubes entering therelevant U- legs preferably onlya short distance.

- The box, 5, is fed from the feed purnp by way of an inner longitudinalpipe, 6, with holes at intervals to give a substantially uniform dis-'tribution of feed along its length, an extension, 6a, of the pipe, 6,leading to the outside of the drum.

It will be understood that the numbers of rows of tubes given above aremerely of an illustrative nature.

The inner wall of the feed-box 5 by means of a plate 5a is in effectextended in a downward direction-so as to make a substantiallyfluid-tight joint with the shell of the drum; it is also extended in anupward direction (Figure 5). V

A longitudinal diaphragm, extending over the whole length of the drum -2is provided between the inner wall of the feed-box and the shell of thedrum so as to separate-the tubes, 0' and D, into two groups. Transversebaffles or plates, 8, 9, (Figures 6 and 7) are also fitted extendingacross the drum to a height somewhat above the water level, the trough,4, which passes a short distance through these diaphragms, being closedat one end by a plate, H], and at the other end by a perforated plate,Illa, through which feed-water is admitted to the interior of thetrough.

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In the form of the invention under descrip- The plate 8 is provided withapertures, 8a (Figure 7) so that the colder water from the tubes, D, maypass to the space, X, at one end of the boiler while the plate, 9, isprovided with apertures, 9a, (Figure 6) so that the warmer feedwaterfrom the tubes, C, may pass to the space, Y, at the other end of theboiler, the water contents of the drum being thus segregated into hotterand less hot parts in such a way that the cooler water is at the end, X,from which the trough, 4, receives water through the perforated plate,Illa.

The hotter water at the opposite end, Y, of the drum may be used to feedthe water walls, I I, of a pulverised coal or Stoker-fired combustionchamber located below the boiler, as shown in Figure 8 the steamproduced in these waterwalled tubes being led to the steam space of thedrum, 2, in the ordinary manner.

The space between the plate, 5a, and the sides of the trough, 4,receives the steam from the tubes of the evaporating bank of tubes,A,'and owing to the fact that this space is shut off by the plates 5aand during normal operation contains no water, circulation is assistedby the absence of a resistance head in the drum. Furtherf more waterreturning from the tubes of bank C cannot flood the steam returning frombank A owing to the physical barrier imposed by the plate 5a.

The tubes of these banks, C and D, are preferably of the U-Field typewith the feed tubes passing a greater or less distance into one leg onlyof these Us.

With the boiler described, cold feed enters by the pipes, 6, Go, intothe feed-box '5, and passes through the inner tubes of the banks oftubes, 0 and D, and round the return bends of the Field tubes. 7 l

Owing to the longitudinal baillefl, the water returned from the bank, D,passes to the end, X, of the boiler and thence through the perforatedplate, Illa, to the space within the trough, 4, and so down the innertubes of the bank of Field tubes, A, steam generated in this bank beingdelivered into the free space between the plate, 5a, and the adjacentside of the trough, 4, whence it escapes to the steam space of theboiler; while the hotter feed from the bank of tubes, C', passes to theother end, Y, of the boileiand thence in the case described above to thewall tubes l I (Figure 8) of the pulverised fuel boiler, the steamgenerated in which is led to the steam space of the drum. i r Thefeed-box, 5, within the main drum is under pressure, the outer tubesserving merely as a feed-water heater or economiser, or as'regards thosetubes nearer the furnace possibly asa steaming economiser. H b

By virtue of the invention, it will be seen that owing to the manner inwhich the cold feed passes" through from the feed boxes 5 by way of thefeed tubes 3a into the outermost rows of tubes, the latter are'kept at acomparatively low tem-' perature.

In this way, taking advantage of the properties of a U-tube fed in theleg more remote from the furnace, in conjunction with high gasvelocities obtained by the progressive reduction of the cross-sectionalarea of the gas passages, the rows of tubes more remote from the furnaceare utilised much more efficiently than heretofore and more heat isextracted from the hot gases, thereby lowering their temperaturesufficiently to eliminate or greatly reduce the dimensions of the usualexternal economiser.

This invention is to be contrasted with the general practice inwater-tube boilers, according to which the feed is fed into the body ofwater in one of the drums and rapidly assumes the temperature of thewater therein, so that but little, if any, extra cooling of parts of thetube systemis secured in order to obtain the greater temperaturedifference referred to above on which the increased efiiciency of thepresent boiler depends.

The fact that with a Field-tube single-drum boiler, the ends of thecirculating units are free, makes it possible to use baiiies inaccordance with the present invention even when the tubes of thecirculating units are in staggered relation and closely pitched.

Many variations may be made from the structural details described abovewithout exceeding the scope of the invention.

I claim:

1. A water-tube boiler comprising a furnace, a steam drum, water tubespassing in a downward direction therefrom at different distances fromsaid furnace so that the water in said tubes is at difierenttemperatures, means for dividing said drum into a plurality ofcompartments at least one of which is closed and is fed by comparativelycold feed water, certain of said tubes containing hotter waterdelivering into one of said compartments, certain other of said tubescontaining less hot Water delivering into another of said compartmentsand certainof said tubes being fed by water from said closedcompartment, a combustion chamber having water-walls, and with meansconnecting said compartment containing said hotter Water with said waterwalls.

2. A water-tube boiler comprising a furnace, a steam drum, water tubespassing in a downward direction therefrom at dififerent distances fromsaid furnace so that the water in said tubes is at differenttemperatures, means for dividing said drum into a plurality ofcompartments at least one oi which is closed and is fed by comparativelycold feed water, certain of said tubes containing hotter waterdelivering into one of said compartments, certain other of said tubescontaining less hot water delivering into another of said compartmentsand certain of said tubes being fed by water from said closedcompartment, a combustion chamber having water-walls, and With meansconnecting said compartment containing said hotter water with saidwater-walls and other means connecting said water-walls with said

